The present invention relates to surface wave devices and to monopulse surface radar systems.
In various applications, it is desirable to filter pairs of signals without introducing error in the phase difference between those signals. Further it is desirable to do so with relatively low cost and with reliability in performance.
In monopulse radar systems crystal filters have been employed for this purpose, i.e. to generate accurate phase information about two related target return signals for the purpose of making target calculations. Such filters have been relatively costly to make and their physical size requires relatively large ovens for ovenizing where wide temperature stabilization requirements exist. Further, the signal transfer characteristics of the crystal filters are such that the filtered output signals have relatively long rise and fall times thereby restricting target calculation rates in radar systems.
Surface wave devices have been developed in recent years for filtering and other circuit functions. For example, an article entitled "Surface Waves Emerge From The Lab And Into The Real World" and published by the present inventor in the September 20, 1975 issue of EDN magazine, sets forth general background information on surface wave device developments. Some U.S. patents in this subject matter area include Hartmann 3,755,761 which issued August 28, 1973 and discloses a surface wave transversal frequency filter having multiple filter sections on a common substrate for filtration purposes but not phase correlation purposes; and Whitehouse 3,757,256 which shows a surface wave device having multiple launch electrodes. No known application of surface wave technology has been directed to the phase correlation problem outlined above.